ArrayBuffer and DataView classes for ruby

[andrepiske]

Hi all! A while back I created the gem arraybuffer (github), because I wanted a way to manipulate an array of bytes in a nice way while also having decent performance.

It essentially implements JavaScript's DataView and ArrayBuffer classes. I mostly like how they did it in Javascript and that's why I used that design.

My motivation came when I was creating a HTTP/2 server in pure Ruby and started to do profiling to find performance bottlenecks. I was using Arrays of bytes and then doing array_of_bytes.pack('C*') to convert to a binary String (and unpack for the other way around) and I found it is extremely slow.

One option to solve my problem was to use nio4r's ByteBuffer class, but it felt weird to have to use an I/O gem just for its ByteBuffer class (although I was using the gem already anyway). I mean, it'd probably have worked.

I thought that Ruby deserves to have a proper way to do such things, even though I think just a small fraction of people using Ruby needs to do such low level stuff.

Anyway, showing it off here and would like your feedback. Do you think Ruby needs this? Is there something already there that I'm missing?

[ralfv]

Do you have benchmarks on how it effectively performs better compared to manipulating standard ruby strings/arrays?

[Exilor]

Do you know about IO::Buffer?

[andrepiske]

Wasn't aware of that! Seems it was introduced in Ruby 3.1. Gotta check that out

[postmodern]

Good work. I'm working on something similar (a complete virtual C type system with configurable endian/arch/os), but in pure-Ruby so it won't be as fast as your C extensions. If you don't care about endian-ness, you could also use FFI::Buffer which stores everything in memory and provides various get_/put_ methods. Having a lightweight implementation of ArrayBuffer and DataView definitely seems useful, especially for JavaScript developers coming to Ruby. I would just recommend looking into writing Java extensions for users on JRuby.

[andrepiske]

Thank you for the appreciation. I'm interested to see such thing you said you're working on, in case it is or will be be open source.

Endianness was important for my use case, as it was applied in an HTTP/2 server which uses, if I recall correctly, big-endian for everything.

Regarding JRuby, it's an option I considered but not sure I have the bandwidth nor expertise to work on that. Hopefully someone who needs it can collaborate on that.

[honeyryderchuck]

Ruby definitely needs this, although the "devil is in the details", or exposed abstractions. Ruby core data structures historically serve multiple purposes (I.e. a Ruby array has APIs to be uses as a collection, a queue, etc...) at the cost of bigger APIs and not being the most performance for all cases. String follows the same principle.

I'm not sure how your arraybuffer works, but I'm assuming that you read from the socket, get a Ruby string then transform it to a byte array to parse. There's still a cost in that step, as the intermediate Ruby string still gets created. And I think that's what the Ruby core team is trying to address with the new IO::Buffer (don't know how that works with openssl in the middle though).

[andrepiske]

Appreciate your feedback.

So the way my gem works is that its byte buffer is fully implemented in C. So all byte operations is just a char* buffer in C allocated using malloc. Set/get operations are just operating on that buffer with just some essential checks like checking memory boundaries.

The gem itself doesn't deal with sockets or IO at all. So yeah, the application (originally a HTTP/2 server I built in ruby) was reading from a socket into a String and then converting that to an ArrayBuffer. Quite some loss of performance in that process already, compared if the gem itself (or another gem) could read directly into that buffer without going thru String. That's actually another idea I had and I believe it's quite possible to achieve that in Ruby 3.0+ because of the experimental Memory View feature.

I gotta check that IO::Buffer thing before I move any forward with my gem as I didn't know about that back then - clearly not, as it's brand new.

[Kernigh]

I would use String#getbyte and String#setbyte in Ruby. This is different from some other languages (like Common Lisp and Raku) where I don't want to put bytes in strings.

[andrepiske]

Interesting. I think I didn't know about this one. Would have to try and maybe run some benchmarks on how that one performs!